The present invention relates to golf balls and, more particularly, to improved two-piece golf balls having low spin rates. The improvement in the golf balls results from a combination of a relatively soft core and a hard cover made from blends of one or more specific hard, high stiffness ionomers. The combination of a soft core and a hard cover leads to an improved golf ball having a lower than anticipated spin rate while maintaining the resilience and durability characteristics necessary for repetitive play.
The present invention also pertains to improved multi-layer golf balls having one or more layers containing metal particles or other heavy weight filler materials to enhance the perimeter weight of the balls. Such weighting material may be incorporated in one or more of an inner layer or an outer layer of the ball. Preferably, the heavy weight filler particles are present in an outer cover layer. Most preferably, the weighting material is visible along the exterior of the ball. The inclusion of the particles along with the production of a smaller core produces a greater (or higher) moment of inertia. This results in less spin, reduced slicing and hooking and further distance.
In an additional embodiment of the invention, the spin rate is further reduced by decreasing the weight of the soft core while maintaining core size and by increasing the thickness of the cover. The larger, less dense finished ball exhibits lower spin rates after club impact than conventional balls.
Spin rate is an important golf ball characteristic for both the skilled and unskilled golfer. High spin rates allow for the more skilled golfer, such as PGA professionals and low handicap players, to maximize control of the golf ball. This is particularly beneficial to the more skilled golfer when hitting an approach shot to a green. The ability to intentionally produce xe2x80x9cback spinxe2x80x9d, thereby stopping the ball quickly on the green, and/or xe2x80x9cside spinxe2x80x9d to draw or fade the ball, substantially improves the golfer""s control over the ball. Thus, the more skilled golfer generally prefers a golf ball exhibiting high spin rate properties.
However, a high spin golf ball is not desirous by all golfers, particularly high handicap players who cannot intentionally control the spin of the ball. In this regard, less skilled golfers, have, among others, two substantial obstacles to improving their game: slicing and hooking. When a club head meets a ball, an unintentional side spin is often imparted which sends the ball off its intended course. The side spin reduces one""s control over the ball as well as the distance the ball will travel. As a result, unwanted strokes are added to the game.
Consequently, while the more skilled golfer desires a high spin golf ball, a more efficient ball for the less skilled player is a golf ball that exhibits low spin properties. The low spin ball reduces slicing and hooking and enhances roll distance for the amateur golfer.
The present inventors have addressed the need for developing a golf ball having a reduced spin rate after club impact, while at the same time maintaining durability, playability and resiliency characteristics needed for repeated use. The reduced spin rate golf ball of the present invention meets the rules and regulations established by the United States Golf Association (U.S.G.A.).
Along these lines, the U.S.G.A. has set forth five (5) specific regulations to which a golf ball must conform. The U.S.G.A. rules require that a ball be no smaller than 1.680 inches in diameter. However, notwithstanding this restriction, there is no specific limitation as to the maximum permissible diameter of a golf ball. As a result, a golf ball can be as large as desired so long as it is larger than 1.680 inches in diameter and so long as the other four (4) specific regulations are met.
The U.S.G.A. rules also require that balls weigh no more than 1.620 ounces, and that their initial velocity may not exceed 250 feet per second with a maximum tolerance of 2%, or up to 255 ft./sec. Further, the U.S.G.A. rules state that a ball may not travel a distance greater than 280 yards with a test tolerance of 6% when hit by the U.S.G.A. outdoor driving machine under specific conditions.
It has been determined by the present inventors that the combination of a relatively soft core (i.e. Riehle compression of about 75 to 115) and a hard cover (i.e. Shore D hardness of 65 or more) significantly reduces the overall spin rate of the resulting two piece golf ball. The inventors have also learned that an increase in cover thickness, thereby increasing the overall diameter of the resulting molded golf ball, further reduces spin rate.
Top-grade golf balls sold in the United States may be generally classified as one of two types: two-piece or three-piece balls. The two-piece ball, exemplified by the balls sold by Spalding and Evenflo Companies, Inc. (the assignee of the present invention through its wholly owned subsidiary, Lisco, Inc.) under the trademark TOP-FLITE, consists of a solid polymeric core and a separately formed outer cover. The so-called three-piece balls, exemplified by the balls sold under the trademark TITLEIST by the Acushnet Company, consist of a liquid (e.g., TITLEIST TOUR 384) or solid (e.g., TITLEIST DT) center, elastomeric thread windings about the center, and a cover.
Spalding""s two-piece golf balls are produced by molding a natural (balata) or synthetic (i.e. thermoplastic resin such as an ionomer resin) polymeric cover composition around a preformed polybutadiene (rubber) core. During the molding process, the desired dimple pattern is molded into the cover material. In order to reduce the number of coating steps involved in the finishing of the golf balls, a color pigment or dye and, in many instances, an optical brightener, are added directly to the generally xe2x80x9coff whitexe2x80x9d colored polymeric cover composition prior to molding. By incorporating the pigment and/or optical brightener in the cover composition molded onto the golf ball core, this process eliminates the need for a supplemental pigmented painting step in order to produce a white or colored (notably orange, pink and yellow) golf ball.
With respect to multi-layered golf balls, Spalding is the leading manufacturer of two-piece golf balls in the world. Spalding manufactures over sixty (60) different types of two-piece balls which vary distinctly in such properties as playability (i.e. spin rate, compression, feel, etc.), travel distance (initial velocity, C.O.R., etc.), durability (impact, cut and weather resistance) and appearance (i.e. whiteness, reflectance, yellowness, etc.) depending upon the ball""s core, cover and coating materials, as well as the ball""s surface configuration (i.e. dimple pattern). Consequently, Spalding""s two-piece golf balls offer both the amateur and professional golfer a variety of performance characteristics to suit an individual""s game.
In regard to the specific components of a golf ball, although the nature of the cover can, in certain instances, make a significant contribution to the overall feel, spin (control), coefficient of restitution (C.O.R.) and initial velocity of a ball (see, for example, U.S. Pat. No. 3,819,768 to Molitor), the initial velocity of two-piece and three-piece balls is determined mainly by the coefficient of restitution of the core. The coefficient of restitution of the core of wound (i.e. three-piece) balls can be controlled within limits by regulating the winding tension and the thread and center composition. With respect to two-piece balls, the coefficient of restitution of the core is a function of the properties of the elastomer composition from which it is made.
The cover component of a golf ball is particularly influential in effecting the compression (feel), spin rates (control), distance (C.O.R.), and durability (i.e. impact resistance, etc.) of the resulting ball. Various cover compositions have been developed by Spalding and others in order to optimize the desired properties of the resulting golf balls.
Over the last twenty (20) years, improvements in cover and core material formulations and changes in dimple patterns have more or less continually improved golf ball distance. Top-grade golf balls, however, must meet several other important design criteria. To successfully compete in today""s golf ball market, a golf ball should be resistant to cutting and must be finished well; it should hold a line in putting and should have good click and feel. In addition, the ball should exhibit spin and control properties dictated by the skill and experience of the end user.
A low spin ball is generally preferred, particularly for the less skilled player. And, increasing the moment of inertia of the ball tends to reduce the spin rate of the ball. The present invention provides a remarkable and unique approach for readily increasing the moment of inertia of a golf ball. The approach of the present invention is economical and easily implemented in large scale commercial golf ball manufacturing processes.
In an alternative embodiment, the spin rate of the ball is further reduced by increasing the thickness of the cover and/or decreasing the weight and softness of the core. By increasing the cover thickness and/or the overall diameter of the resulting molded golf ball, enhanced reduction in spin rate is observed.
With respect to the increased size of the ball, over the years golf ball manufacturers have generally produced golf balls at or around the minimum size and maximum weight specifications set forth by the U.S.G.A. There have, however, been exceptions, particularly in connection with the manufacture of golf balls for teaching aids. For example, oversized, overweight (and thus unauthorized) golf balls have been on sale for use as golf teaching aids (see U.S. Pat. No. 3,201,384 to Barber).
Oversized golf balls are also disclosed in New Zealand Patent 192,618 dated Jan. 1, 1980, issued to a predecessor of the present assignee. This patent teaches an oversize golf ball having a diameter between 1.700 and 1.730 inches and an oversized core of resilient material (i.e. about 1.585 to 1.595 inches in diameter) so as to increase the coefficient of restitution. Additionally, the patent discloses that the ball should include a cover having a thickness less than the cover thickness of conventional balls (i.e. a cover thickness of about 0.050 inches as opposed to 0.090 inches for conventional two-piece balls).
In addition, it is also noted that golf balls made by Spalding in 1915 were of a diameter ranging from 1.630 inches to 1.710 inches. As the diameter of the ball increased, the weight of the ball also increased. These balls were comprised of covers made up of balata/gutta percha and cores made from solid rubber or liquid sacs and wound with elastic thread.
Golf balls known as the LYNX JUMBO were also commercially available by Lynx in October, 1979. These balls had a diameter of 1.76 to 1.80 inches. The LYNX JUMBO balls met with little or no commercial success. The LYNX JUMBO balls consisted of a core comprised of wound core and a cover comprised of natural or synthetic balata.
However, notwithstanding the enhanced diameters of these golf balls, none of these balls produced the enhanced spin reduction characteristics and overall playability, distance and durability properties of the present invention and/or fall within the regulations set forth by the U.S.G.A. An object of the present invention is to produce a U.S.G.A. regulation golf ball having improved low spin properties while maintaining the resilience and durability characteristics necessary for repetitive play.
These and other objects and features of the invention will be apparent from the following summary and description of the invention and from the claims.
The present invention is directed to improved golf balls having a low rate of spin upon club impact. The golf balls comprise a soft core and a hard cover. The core has a Riehle compression of at least about 75, and preferably 75 to about 115. The cover has a Shore D hardness of at least about 65. The golf balls generally comprise a core and an outer layer, the outer layer including at least one discrete region of a weighting material that serves to increase the moment of inertia of the golf ball.
In a first aspect, the present invention provides a golf ball comprising a core having a Riehle compression of at least 75, and a layer disposed about the core that has a Shore D hardness of at least about 65. The layer includes at least one region of weighting material, and at least one other region of layer material less dense than the weighting material.
In another aspect, the present invention provides a golf ball comprising a core having a Riehle compression of at least about 75, and an outer layer disposed around the core. The outer layer includes at least one discrete region of a weighting material that serves to increase the moment of inertia of the ball. And, at least one region of the weighting material is visible along the exterior of the golf ball. The outer layer has a Shore D hardness of at least about 65.
In yet another aspect, the present invention provides a multi-layer golf ball having an increased moment of inertia. The golf ball comprises a core having a Riehle compression of from about 75 to about 115. The core further comprises an inner layer disposed about the core, and an outer layer disposed about the inner layer. The outer layer has a Shore D hardness of at least about 65. The golf ball further comprises an effective amount of a weighting material disposed in at least one of the inner layer or the outer layer.
Through the use of the softer cores and the hard cover, overall finished balls of the invention exhibit significantly lower spin rates than conventional balls of equal size and weight. Further, reduction in spin is also produced by increasing the thickness of the cover and by decreasing the weight of the softened core.
Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. It should, however, be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art.